Grinding disk



May 8, 1956 J F, BEHRENDT ET AL 2,744,364

GRINDING DISK Filed Dec. 1, 1954 INVENTORS.

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2,744,364 GRINDING DISK Julian 5F. Behrendt and Ignatius F. Behrendt, Cicero, Ill.

Application December 1, 1954, Serial No. 472,352' 6 Claims. (Cl. 51-197,)

This invention relates to improvements in abrasive disc grinding, sanding or finishing'machines, and more particularly to the means for securing the abrasive coated cloth disc thereto, and to the method of forming the abrasive coated cloth disc.

One of the objects of this invention is to provide an abrasive coated cloth disc for a grinding, sanding or finishing machine which will be positively secured to the backing plate in such a manner that it will not scale off or become detached or separated from said backingplate.

Another object of this invention is to provide a new and improved abrasive disc and backing plate secured together in such a manner that the abrasive disc may be rotated at a greater speed than heretofore and whichmay be operated at an increased speed of approximately 18,000 feet per minute at the perimeter and used effectively as an abrasive element without causing the abrasive coated cloth disc to scale or otherwise become detached from the backing plate.

It is recognized in the industry that the abrasive discs now on the market are limited in that the disc must'be operated at speeds not exceeding approximately 10,000 feet per minute at the perimeter. And that the abrasive element scales or becomes detached from the backing plate due to frictional heat created by work contact or centrifugal force, thereby reducing the productive value of the disc as well as creating a hazard to safe operation.

It is to overcome these objections of the present day construction that this invention is directed. With this invention it will be seen and recognized that the abrasive coated cloth disc is secured to the backing plate .in a positive manner, such net the abrasive coated'cloth disc may be operated at a much greater speed. than heretofore and yet at the same time the abrasive coated cloth disc will not scale or become detached or separated from the backing plate due to frictional heat or centrifugal force. It will also be recognized that with the increased speed made possible by this invention (18,000 feet per minute at the perimeter), will enable greater production, finer finishes (even with coarser abrasives), and reduced manual fatigue.

Another object is to provide a method of forming abrasive coated cloth discs.

Other objects will become apparent as this description progresses.

In the drawings:

Fig. .1 is a face or front view of the abrasive coated cloth disc. 7

Fig. 2 is a detail on line 22 of Fig. 1 showing the abrasive coated cloth disc.

Fig. 3 is a cross-sectional view of the assembly and mounting unit and showing the abrasive coated :cloth disc secured thereto.

Fig. 4 is an exploded elevational view of the parts shown in Fig. 3 drawn to asmaller scale, and

Fig. Sis a front view of a detail lookingin the direction of line 5-5 of Fig. 3.

"Patented Ma 's, 1956 Referring to the drawings, the numeral 10 designates the rotating shaft which may be secured to a motor or any other source of rotation. Mounted on said shaft to rotate therewith is a flanged hub generally designated by theynumeral 12 which is keyed to said shaft by a key '14 and which is secured'against axial movement on said shaft by a set screw 16,which extends through the hub 18. The flanged portion '20 is shaped like an annular disc and has a-central'openin'g 22 communicating with the bore of the hub. The face of the flanged portion 20 has an annular shoulder 24. An annular'steel plate or backing member shown in'Fig. 3 'to detachably secure the backing member to the flanged hub.

The backing member may thus be readily secured to and detached from thefianged hub and rotates therewith upon therotation of the rotating shaft 10.

The backing plate 26 adjacent the central opening 28 has an inclined or tapered wall 33'which extends from the outer face of the backing plate to the longitudinal wall 40 .of the central opening 28 with the backing plate secured'to the flanged hub as shown in Fig. 3 the inclined wall 33 with 'the't'ront vertical section 25 of the shoulder 24 forms a recessed pocket for receiving the depressed portion. of the abrasive coated cloth disc presently to be described.

The abrasive 'coated'cloth disc which is secured to the backing plate 26 is designated generally by the numeral 42 and said abrasive coated cloth disc comprises an abrasive face 44 and a depressed portion 46. The depressed portion has 'an inclined wall 48 and a circular vertical section 50 which terminates in an annular opening 52 of the same circumference as the opening of the flanged hub. The inclined wall 48 of said abrasive coated cloth disc .is complementary to the shape of the inclined wall of the backing plate 26 and is adapted to be positioned against said backing plate.

The centering member generally designated by the numeral 54 serves both -to center the abrasive coated cloth disc 42 as Well as to apply pressure to said abrasive coated cloth disc and hold it against the backing plate 26. 'The centering member comprises an annular hubportion 56 having an annular flange head '58 which is provided with an inclined or tapered surface 60 and a vertical section 62. The hub 56 has an annular bore '64 which communicates with an enlarged flared opening 66 in the head of the centering member. The tapered wall 60 of. the centering member is complementary to the tapered section 48 of the abrasive coated cloth disc and the tapered or inclined section of the backing member and when the abrasive coated cloth disc 42 is positioned on the backing plate and the centering member applied it will be seen that the tapered section 48 of the abrasive coated cloth disc is positioned between the centering member and the backing plate.

A locking nut generally designated by the numeral 66 is inserted in the central opening of the centering member 54 and said locking nut has a tapered head 68, complementary to the shape of the flared opening of the centering member and rests thereagainst. The hub 70 of the locking nut is confined in the central opening of the centering member 54. The locking nut 66 has a central threaded bore 72 and .a hexagonal shaped opening 73. A threaded stud 74 is in threaded engagement with the bore 72 and extends rearwardly to be secured to the threaded bore 11 of the rotating shaft 10. The stud 74 has a slot 75.

The abrasive coated cloth disc 42 is first secured to the backing plate 26 by means of a suitable adhesive 76 which completely covers the back of the disc. It will thus be seen that the entire back surface of the disc is bonded to the backing plate 26 and the center of the abrasive coated cloth disc is secured to the backing plate by means of the centering and pressure plate 54. With this arrangement we have found that the abrasive coated cloth disc can be rotated at approximately 18,000 feet per minute at the perimeter and with this method of centering and retaining the abrasive, the abrasive coated cloth disc will not scale or become detached from the backing plate when the abrasive coated cloth disc is being used. With prior devices it would be impossible to operate the abrasive coated cloth disc at this speed or even at much lower speeds without scaling or detaching the abrasive coated cloth disc from its backing plate.

The method of forming the depressed portion in the abrasive coated cloth disc will now be described. The forming of the depressed center portion of the abrasive coated cloth disc can only be done after the abrasive has been bonded to the cloth in the usual manner. The abrasive coated cloth disc is placed between two metal plates the size of the disc. The plates have a large hole in the center to permit the entrance of a die for the purpose of forming the depressed portion 46 in the abrasive coated cloth disc. These metal plates and dies are preheated to a temperature of from 200 to 250 degrees F. Pressure is applied to the heated plates which hold the material firmly in place so that when pressure is applied to the depression forming die, all stretch in the material will be uniform. As the heated plates and die soften the bonding material of the abrasive coated cloth disc all distortion is confined to the depressed area. While holding the abrasive coated cloth disc between pressure plates and the die with the pressure applied to both, the annular opening 52 in the abrasive coated cloth disc is formed by a plunger located in the center of the die. By this process of forming, the opening 52 and the depressed portion 46 is proportionately true with the perimeter of the abrasive coated cloth disc. The abrasive coated cloth disc is next removed from between the pressure plates and die and allowed to cool. After cooling the depressed portion is rigid without any deformity to the rest of the abrasive coated cloth disc.

An abrasive coated cloth disc of itself is old in the art and forms no part of this invention. Such discs are first formed of a cloth having abrasive material of varying grits bonded to it by glue, resin and/or combination glue and resin bond. Such abrasive coated cloth discs are sold by Minnesota Mining 8: Manufacturing Co. under such brand names as 3 M-Garnet, Three-M-Ite and Tri- M-Ite. Similar discs are sold by the Carborundum Co. and others.

Likewise it is old to attach the above mentioned abrasive coated cloth discs to a backing member by a bonding material. However, the use of such prior art structure has been objectionable in that the abrasive coated cloth discs had to be operated at much lower speeds than that accomplished by this invention and even at much lower speeds the disc would scale and would become detached from the backing member due to frictional heat or centrif ugal force. With this invention the objectionable features of the prior art constructions are eliminated and the objects heretofore set forth are attained.

With this invention the abrasive coated cloth disc is used for grinding or removal of practically any commercial type of metal, wood, hide, glass, stone, plastic, ceramic and the like and it is possible to hone or fine finish these materials. It is well understood that the method of grinding, sanding or finishing materials on this machine is accomplished by pressing the materials against the abrasive coated cloth disc as same is rotating at a high speed.

It will be understood that various changes and modifications may be made without departing from the spirit and scope of the appended claims.

We claim:

1. In an abrasive device comprising a rotating shaft, a flanged hub secured thereto to rotate therewith, a metal backing plate having a fiat surface, said backing plate being secured to said flanged hub, said backing plate having a central opening and a tapered wall adjacent said opening, an abrasive coated cloth disc bonded to the flat surface of said metal backing plate, said abrasive disc having an annular depressed portion and a central opening in said depressed portion, said depressed portion having an outer wall complementary to the tapered wall of said backing plate so that same is positioned thereagainst, a centering member adapted to nest within said depressed portion and means for securing said centering member to said rotating shaft.

2. In an abrasive device comprising a rotating shaft, a flanged hub secured thereto to rotate therewith, a rigid supporting plate having a flat surface secured to said flanged hub, said supporting plate having a central opening and a tapered wall adjacent said opening, an abrasive coated cloth disc bonded to said flat surface of said supporting plate, said abrasive coated cloth disc having an annular depressed portion and a central opening with said depressed portion having an outer wall complementary to the tapered wall of said supporting plate and adapted to be positioned thereagainst, a centering member adapted to nest within said depressed portion, and means for securing said centering member to said rotating shalt.

3. In an abrasive device comprising a rotating shaft, a flanged hub secured thereto to rotate therewith, a rigid backing plate secured to said flanged hub, said backing plate having a central opening and a tapered wall adjacent said opening, an abrasive coated cloth disc adhesively secured to said rigid backing plate, said disc having an annular depressed portion and a central opening with said depressed portion having an outer wall complementary to the tapered wall of said backing plate, a centering member having an annular hub adapted to be received within the opening of the abrasive coated cloth disc, said centering member having a tapered wall complementary to the tapered wall of said abrasive coated cloth disc and adapted to rest thereagainst, and means for securing said centering member to said rotating shaft.

4. In an abrasive device comprising a rotating shaft, 21 flanged hub secured thereto to rotate therewith, a metal backing plate secured to said flanged hub, said backing plate having a central opening and a tapered wall adjacent said opening, an abrasive coated cloth disc bonded to said metal backing plate, said abrasive disc having an annular depressed portion and a central opening with said depressed portion having an outer wall complementary to the tapered wall of said backing plate, a centering member having an annular hub adapted to be received within the opening of the abrasive coated cloth disc, said centering member having a tapered wall complementary to the tapered wall of said abrasive coated cloth disc and adapted to rest thereagainst, means for securing said centering member to said rotating shaft, and a locking nut for securing said centering member to said rotating shaft.

5. In an abrasive device comprising a rotating shaft, a flanged hub secured thereto to rotate therewith, a rigid backing plate detachably secured to said flanged hub, said backing plate having a central opening and a tapered wall adjacent said opening, an abrasive coated cloth disc bonded to said rigid backing plate, said disc having an annular depressed portion and a central opening with said depressed portion having an outer wall complementary to the tapered wall of said backing plate, and a centering member adapted to nest within said depressed portion and secured to said rotating shaft.

5 6 6. In combination a rotatable flat metal backing mem- References Cited in the file of this patent her having a flat surface, said backing member having a UNITED STATES PATENTS central opening and a tapered wall ad acent said openlng,

an abrasive disc bonded to the flat surface of said metal 1,648,663 Stratford -"r- 1927 backing member, said abrasive disc having an annular 5 1686938 Stmtford 1928 depressed portion and a central opening in said depressed 1938493 Myers 51 1933 portion, said depressed portion having an outer wall com- 2370323 1945 plementary to the wall of said backing member so that 6 81 1946 same is positioned thereagainst, a centering member adapted to nest within said depressed portion and hold said 10 abrasive disc against said backing member. 

